Antivibration gear drive



Dec. 22, 1953 F. R. GR-UNER 2,663,201

ANTIVIBRATION GEAR DRIVE Filed Dec. 25, 1949 Patented Dec. 22, 1953 Frederick R. Gruner,

West Allis, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application December 23, 1949, Serial No. 134,685 6 Claims. (01. 74665) This invention relates to antivibration toothed gear drives, particularly adapted for rotating a kiln shell. A principal object of the invention is the provision of new and improved toothed gear drives of these types.

Theadoption of modern increased kiln dimensions and greater rotational kiln speeds presents serious vibrational problems which may become destructive under certain circumstances. An illustration of) the vibrational dif ficulties encountered with modern units may be shown by Way or example only; usinga kiln rotating at a critical speed (hefreingdefined as-that speed at which resonance occurs) of one revolution per minute and driven with a main gear having 200 teeth engagements per inute. Since the ratio of the teeth in the main gear to the teeth in the driving pinion .is usually large. in the order of ten to one, the variation in torque transmission becomes appreciable. Should the natural vibrational. frequency of the kiln and the drive ap: proach .200 vibrations pier minute,v the vibrational amplitudes of, the system vwill ,become dangerously large. This excessive vibratory efiect has been somewhatreducedzin the vadoption of, a dual drive system. In. a dual :pinion drive finer pitch gears may be used. instead of the coarse ipitch gears in :a. single pinion drive, to, result. in smoother torquetransmiss-ion. rResonance nevertheless may still occur and, hence-it is a further object of this inventiontoflprovide' a. positive i means forobviating' this undesirable excessive vibrational efiectl H n i Other objects will appearghereinafter as the description of theinvention proceeds.

.The novel features of the invention and how the objects are attained will appear from. thisspecification and the accompanying drawing showing several embodiments of .thesinvention and vforming a. part of this? application, and all, of these novel: features areintended to be pointed out in the claims.

In'the drawing-Ln-..

, Fig. l. is'a side; ell: ,aitional view partly in section showing one torque-transmitting drive Fig. 2 isan enlarged fragmentary end view of gearing embodyingimyinvention;

Fig. 3- is a graphie'alzshowingcomparing the vibrational wavesv set :up in. rotating a kiln shell, when usinga dual pinion drive according to my invention, and a-conventional single pinion drive;

Fig. 4 is a diagrammatic illustration of a four pinion drive; and V V Y Fig. 5 is a graphical: showing zofethenvibrational'wavesiprodu'cediiin:a; drive as illustrated in Fig; 4.

' embodiment of the invention is herein shown'in Figs. 2, 3 as applied to a dual pinion drive transmission designated by gear means such as driving pinions 5; 6, for rotating a kiln shell. Howevenany number of pinion's as may be practical for operation may be used in the practice of my invention, not only adapted for rotating a kiln shell, but for rotating any elongated member supported for rotation about its longitudinal axis.

Fig. 1 illustrates a suitable drive or torque transmitting unit for rotating one of the driving pinions, incorporated in the teaching of my nv n on. inv his i sta ce pinion 6, andis rep.- resentative of similar independent dr've units for respectively driving the other or remaining drivmg p1n10ns. U

The torque transmitting unit ,comprisesgabearing support, .hereinshown as .audouble bearing pedestal torrotatably receiving a pinion shaft the armature shaft 20-01 the motor Hot l. One

end .of the high-sheid s haft I4 is supportedas drooping Operating characteristic, more fully describedin theoperationlbf myi venubn. Supported for rotation about its longitudinal effects createdin meshing a. spur gear having a large-number of ;teeth with a spur gear havtime with the latter two gears than with spur gears.

Fig. 2 clearly shows one tures or my invention as applied to a dual pinion drive transmission. The driving pinions 5, 6, mounted on the shafts 8b and 8a, respectively, are circumferentially spaced about the main gear 23, and meshingly engageable therewith for rotating the kiln shell 2| about its longitudinal axis. An angle or defined by radial lines 24, 25 extended from the center of the kiln shell 2| and expressed in degrees by the formula where 5 is an angle defining the circular tooth pitch of the main gear 23 in degrees, a is any integer within reasonable construction limits, and n is the number of driving pinions, determines the angle the axes of the driving pinions are circumferentially spaced apart with respect to each other. Hence the driving pinions 5, 6 are staggered for engagement with the main gear 23 of the principal teaare degrees 01 circular tooth pitch with respect to each other. A specific example illustrated by Fig. 2 may be as follows: where 5:6", 11:14 and n=2; hence w=8'1. Obviously a could theoretically equal zero for the operation of my invention, but in practice the space interference of the driving pinions would eliminate such possibility without an axial displacement of at least on of the driving pinions with respect to the other while simultaneously meshed with the main gear. Conversely a could equal twenty-eight or any other large integer but this would present a supporting problem for at least one or both driving pinions. Therefore a. is preferably chosen within reasonable practical limits to obtain a desired circumferential separation of the pinions.

The operation of my invention may be graphically illustrated by reference to Fig. 3, wherein the vibrations or nonuniform torque transmissions produced by the meshing engagement of the teeth of the main gear 23 with the driving pinions 5, 6, are substantially herein shown as sine waves. The ordinate represents the ampli tude of variation in torque transmission produced from engagement of the driving pinions with the main gear, and the abscissa a period of vibration which is directly proportional to the speed of rotation of the kiln 2|.

Sine wave 26 is representative of the vibration created with a single driving pinion (not shown), and sine waves 21, 28 are representative of the vibrations created in the adoption of the dual pinion drive transmission herein illustrated. By using the dual pinion drive the torque input per drive is reduced to fifty percent of the torque input required to rotate the kiln when a single pinion drive is used, and hence the amplitude of vibration is accordingly reduced fifty percent.

As the'driving pinions 5, 6 engage with the main gear 23 for rotation thereof as taught by my invention, each driving pinion will produce the respective sine waves 21, 28 180 degrees out of phase with each other, due to the staggered pinions 30,.3I

'or driving pinion 30, is

circumferential spacing of the driving pinions with the main gear. Hence the sine wave 21 cancels the sine wave 28, or conversely, the sine wave 28 cancels the sine wave 21.

Fig. l shows another embodiment of my invention adopting more than one pair of driving pinions and as herein shown as two pairs, designated by reference characters 3!], 3| and 32, 33. The driving pinions 3|), 3|, 32, 33 may be circumferentially spaced for engagement with a main gear 23a. to degrees, as expressed by the formula (where p is the circular tooth pitch in degrees of the main gear 23a) described and explained with respect to the preferred embodiment illustrated in Figs. 2 and 3, and need not be further enlarged upon. I

Sine waves 35, 36, 31, 38, respectively, represent th vibrational effects created by the engagement of the driving pinions 30, 3|, 32, 33 with the main gear 23a. With the adoption of four driving pinions the torque input per drive is reduced to twenty-five percent of the torque input required to rotate the kiln when a single pinion drive is used, and hence the amplitudes of vibration are accordingly reduced to twentyfive percent. This is clearly seen in comparing the vibrational amplitudes of the sine wave 26 with the sine waves 35, 36 31, 38. Since the driving pinions 33, 3|, 32, 33 are staggered with respect to each other, it is evident from Fig. 5 that two of the driving pinions are degrees out of phase with the other two driving pinions. As herein shown the sine wave 35, 180 degrees out of phase with the sine wave-31, or driving pinion 32, and the sine wave 3t, or driving pinion 3|, is 180 degrees out of phase with the sine wave 38, or driving pinion 33, therefore resulting in a zero torque variation as designated by a straight line resultant 39. Although this hereinabove out of phase sine wave relationship is preferable in the adoption of two or more pairs of driving pinions, a zero torque variation can also be effected by placing one-half of the pinions, in this instance 3|], 3|, in phase or circumferentially arranged 5 degrees with respect to each other, and staggering this half of. the driving pinions for engagement with the main gear 23a, one-half a circular tooth pitch with respect to the other half of the driving pinions 32, 33, where the driving pinions 32, 33 are circumferentially arranged 6 degrees with respect to each other. Since the driving pinions 30, 3| are in phase with each other as are pinions 32, 33, the vibrational effects produced by each one-half of the total driving pinions during operation may be represented by the sine waves 21, 28, respectively, of Fig. 3. That is to say, the sine waves resulting from the inphase coaction of the driving with the main gear 23a are additive and their resultant sum is equal to a sine wave produced by one driving pinion such as 5 of the dual drive system. Similarly the sine waves resulting from the coaction of driving pinions 32, 33 with the main gear 23a are additive and hence equal to a sine wave produced by one driving pinion such as 6 of the dual drive system.

Obviously the position of the respective drivscream ing pinionssti, 3 I, 32," '33 about theinain gear is immaterial, provided they are staggered in relationship with respect toeach other, or onehalf of the driving pinions are-staggered in relationship with respect to -the remaining half of th driving pinions. That is to say, a zero variation or a straight line resultant such as 29 or 39 nevertheless results, if, for example, pinion 3| would be positioned for engagement somewhere between driving pinion 30 and driving pinion 33 instead of between driving pinions 30 and 32, as herein shown.

Whenever anyodd number f pinions, such as three, five, seven, etc, is used in the combination, the vibrational amplitudes are, respectively, proportionately diminished, but a resultant periodic reduced vibratory wave (not shown) will result, which is obviously not as desirable as a. zero variation herein shown asa straight line resultant 29 or 39, as developed when any even number of pinions are meshed with the main gear 23 in accordance with the for 1119. herein previously set forth.

B varying the stiffness of the pinion shafts 8a and 8?) or the low speed shaft l3 or both, and/or the flexible coupling l2, it is possible to change the critical speed above or below the maximum operating rotational speed of the kiln 2|, to further diminish excessive vibrational amplitudes. In extremely long kilns, usually 300 feet or more, it is therefore preferable to lower the critical speed by interconnecting the pinion shaft 8a (or shaft 812) and the low speed shaft l3 with a flexible coupling :12 having a very low stiffness.

Antivibrational performance of the transmission drive will be improved by the drooping characteristics of the motors Ila and [lb obtained by compound wound motors in which the series field adds to the shunt field, or any other known suitable type having only fair regulation, capable of alternately equally sharing the work required to drive the kiln, that is to say, as one of the motors, for example Ha, slows down because of a heavy increase in load, the other motor I lb will speed up until it assumes part of the burden of motor Ila, at which time it will slow down and motor Ila will again speed up. This fluctuation continues as long as the kiln is being rotated, and hence by suitable design of motor characteristics the load distribution on the driving motors can be made substantiall equal.

From the foregoing it will be apparent to those skilled in the art that the illustrated embodiments of the invention provide new and improved antivibration gear drive systems for rotary kilns and the like, and accordingly accomplish the objects of the invention. On the other hand, it will also be obvious to those skilled in the art that the illustrated embodiments of the invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of the invention, or sacrificing all of the advantages thereof, and that accordingly the disclosures herein are illustrative only, and the invention is not limited thereto.

It is claimed and desired to secure by Letters Patent:

1. In an antivibration toothed gear drive. the

plying n additive driving forces to said driven gear (where n is an integer-greater than one), said gear means comprising a series of n driving pinions mounted in spaced circumferential relation to said driven gear forrotation' about respective pinion axes; said pinions being rotatable in fixed out-of-phase relation to each other with reference to lines drawn through said first axis and said respectiv pinion axes an amount equal to circular tooth pitch of'one'of said pinions.

2. In an antivibration toothed gear drive, an externally toothed'driven gear rotatableabout a first axis, and gear means meshed continually with andsimultaneously applying n additive drivsaid driven gear (where n is any even integer), said gear means comprising 12. driving pi'nions mounted for rotation about respective pinion axes spaced 'circumferentially about said driven gear, said pinions be'ing rotatable in fixed out-of-phase relation to each other with reference to lines drawn through said first axis and said respective pinion axes an amount equal to mg forces to said driven gear, said gear means ions being rotatable in fixed out-of-phase relation to each other with reference to lines drawn pitch of one of said pinions.

4. In an antivibration toothed gear drive, an

externally toothed driven gear rotatable about a first axis, and means meshed continually with a t tre -titansan extmaiiyaeaiea driverl gear rotatable about-"a first 1 axis, and gear means meshed continually with and simultaneously apdriven gear for rotation about respective pinion axes, the pinions of each set bein ota le in fixed in-phase relatiorr in each other with reference to lines drawn through said first axis and said pinion axes of said each set, and the pinions of one set being rotatable in fixed out-of-phase relation with the pinions of another set with reference to lines drawnthrough said first axis and said pinion axes of said one and another sets an amount equal to circular tooth pitch of one of said pinions.

6. In an antivibration-toothed spur gear drive, the combination of an externally toothed driven spur gear rotatable about a first axis, gear means meshed continually with and simultaneously apcircular tooth pitch of one ofsaid pinions, and individual motor means; coupled to each of said pinions in power transmitting relation, each said motor means having a drooping characteristic for so apportioning said driving forces between said pinions that the average value of each said driving force is substantially equal to of the sum of said additive driving forces.

FREDERICK R. GRUNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,181,717 Alquist Mar. 2, 1916 1,347,094 Harland July 20, 1920 1,351,717 Bertels Oct. 5, 1920 1,644,222 Baker Oct. 4, 1927 2,257,034 Bugati Sept. 23, 1941 2,260,009 Doran et al Oct. 21, 1941 2,396,057 Petersen Mar. 5, 1946 2,441,901 Petersen May 18, 1948 2,475,329 Leathers et al. July 5, 1949 FOREIGN PATENTS Number Country Date 562,239 Great Britain June 23, 1944 

